A 25-year-old man underwent a renal biopsy for further evaluation after abnormalities in his urinalysis were identified during a routine health check-up.
Past Medical History: None
Medications: None
Family History: His father has a history of renal dysfunction.
Vital parameters:
BP: 119/67 mmHg
HR: 68/min
SpO2: 99 %
Physical Examination:
Physical examination revealed no abnormalities.
Laboratory Findings:
Urinalysis:
RBCs: 10–19/HPF, WBCs: 1–4/HPF, 24-hour urine protein: 1100 mg/day
Blood Tests:
WBC: 5,700/μL, Hb: 14.9 g/dL, Platelets: 253,000/μL, TP: 6.9 g/dL, Alb: 4.2 g/dL, BUN: 11.8 mg/dL, Cr: 1.00 mg/dL, eGFR: 29.6 mL/min/1.73 m², HbA1c: 5.8%, CRP: 0.01 mg/dL, IgG: 1273 mg/dL, IgA: 341 mg/dL, IgM: 100 mg/dL, C3: 91 mg/dL, C4: 51 mg/dL, ANA Titer: 1:40 c-ANCA : negative p-ANCA : negative.
Note related to annotations: To avoid obscuring the lesions, the annotations are deliberately positioned close to, but not directly over, the lesion areas.
Pathological diagnosis: Mild diffuse segmental proliferative glomerulonephritis with 1/34 necrotizing lesion, and 1/34 segmental and 1/34 global glomerulosclerosis, IgA nephropathy.
Oxford classification: M0, E0, S1, T0, C1; Japanese classification: H-Grade I A/C.
Light microscopic findings:
One renal cortex and one cortex to medulla specimens contained about 29-34 glomeruli, of which 1 was obsolescent glomerulus. Mild segmental proliferative lesions were observed in 14-17 glomeruli. Mesangial deposits were observed in the mesangial region, and hemispherical deposits protruding from para-mesangial regions were also observed. One glomerulus with severe changes showed the formation of a small necrotic lesion with fibrin deposition. One glomerulus showed small segmental sclerotic lesion, and three, including this one, showed adhesion with Bowman’s capsule.
Tubulointerstitial lesions were observed predominantly around the obsolescent glomeruli, covering approximately 5% of the cortex.
No significant arterio-arteriolosclerotic lesions were observed.
Immunofluorescence study (8 glomeruli):
Positive findings of IgA (++) and C3c (++) were observed as mesangial granular pattern.
IgM (-)
IgG (-)
IgA (2+) mesangial, granular
C1q (-)
C3c (2+) mesangial, granular
C4 (-)
Electron microscopy findings:
Mesangial electron dense deposits were observed in the glomeruli with hemispherical deposits protruding from the para-mesangial regions. Subepithelial and subendothelial deposits were not evident. Slight membranolysis was observed in the glomerular basement membrane, but thinning or thickening of the glomerular basement membrane was not evident.
Pathological diagnosis: Mesangial proliferative lesions with mesangial electron dense deposits were observed. Immunofluorescence study showed positive IgA and C3c as mesangial granular pattern. 1/34 glomeruli showed necrotic lesions, as acute and active lesions. 1/34 glomerulus showed segmental sclerosis and 1/34 glomeruli showed global glomerulosclerosis, as chronic lesions. The pathological diagnosis was IgA nephropathy.
Oxford classification: M0, E0, S1, T0, C1; Japan classification: H-Grade I A/C.
Further Investigations: Deposition of IgA1 lacks galactose in the O‐glycosylated sites in its hinge region (referred as galactose‐deficient IgA1: Gd‐IgA1) in glomeruli was confirmed by immunofluorescence staining using monoclonal antibody (KM55).